Chemoreception is critical for the survival and reproduction of animals.
Except for a reduced group of insects and spiders, the molecular
identity of chemosensory proteins is poorly understood in invertebrates.
Gastropoda is the extant mollusk class with the greatest species
richness, including marine, freshwater, and terrestrial lineages, and
likely, highly diverse chemoreception systems. Here, we performed a
comprehensive comparative genome analysis taking advantage of the
chromosome-level information of two Gastropoda species, one of which
belongs to a lineage that underwent a whole genome duplication event. We
identified thousands of previously uncharacterized chemosensory-related
genes, the majority of them encoding G protein-coupled receptors (GPCR),
mostly organized into clusters distributed across all chromosomes. We
also detected gene families encoding degenerin epithelial sodium
channels (DEG-ENaC), ionotropic receptors (IR), sensory neuron membrane
proteins (SNMP), Niemann–Pick type C2 (NPC2) proteins, and lipocalins,
although much smaller in size. Our phylogenetic analysis of the GPCR
gene family across protostomes revealed: (i) large gene family
expansions in Gastropoda; (ii) clades including members from all
protostomes; and (iii) species-specific clades with a huge number of
receptors. For the first time, we provide new and valuable knowledge
into the evolution of the chemosensory gene families in invertebrates
other than arthropods.